The Drug Abuse Basic Research Program in the Department of Pharmacology of the University of Michigan is composed of established investigators who have independent, but interrelated, interests in problems related to drug abuse. Studies in the monkey colony are concerned with the development of physical dependence to new analgesic drugs, to morphine antagonists and to compounds which have mixed agonist-antagonist properties. Self-administration studies in rhesus monkeys are used to evaluate the reinforcing properties of drug-taking behavior, to study the choices which the animals make when they have the option of working or not working for a drug. Biochemical studies are concerned with the influence of drugs upon neurohumoral transmitters. Drug transport into cells and drug localization in tissues is studied.